Certain prior art systems may attempt to use global positioning system (GPS) receivers to maintain proper spacing between two vehicles during the unloading or transferring of agricultural material between the vehicles. However, such prior art systems can be susceptible to misalignment of the proper spacing because of transient errors or occasional discontinuities in the estimated position of the GPS receivers, among other possibilities. For example, one or more of the GPS receivers may misestimate its position because of electromagnetic interference, multipath propagation of the received satellite signals, intermittent reception of the satellite signals or low received signal strength of the satellite signals, among other things. If the actual relative speed or actual position of the vehicles changes over time for any reason, harvested agricultural material may be misdirected onto the ground, instead of into a storage container of the receiving vehicle. Thus, there is a need for an improved system for managing the unloading of agricultural material from a vehicle to compensate for or address error in the estimated positions or alignment of the vehicles.